Method and apparatus for the balance centering of rotors



Nov. 3, 1964 H. HACK 3,154,973

METHOD AND APPARATUS FOR THE BALANCE CENTERING OF ROTORS Original Filed July 15, 1955 15 Sheets-Sheet 1 Nov. 3, 1964 H. HACK 3, 73

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Nov. 3, 1964 H. HACK 3,154,973

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METHOD AND APPARATUS FOR THE BALANCE CENTERING 0F ROTORS Nov. 3, 1964 15 Sheets-Sheet 15 Original Filed July 15, 1955 Fig. 16a

United States Patent 3,154,973 siETHfiD AND AEPARATUS F'SR THE BALANCE 1 @F RGTGR Heinrich Hack, Darmstadt, Germany, assignor to Carl Sehenck R/iaschinenfabrii; G.m.b.H., Darmstadt, Germany, a corporation of Germany Qontinuation of application Ser. No. 522,335, July 15, E55. This application San. t, 1961, Ser. No. 81,665 Claims priority, application Germany July 16, 1954- 36 tClaims. (ill. 775) My invention relates to the machining of rotating workpieces in the raw, prefabricated or finished state, and in a more particular aspect, to the balance centering of such workpieces, hereinafter briefly called rotors.

This application is a continuation of my copending application Serial No. 522,335, filed July 15, 1955, and now abandoned.

Assume that a body is rotating in free space. Then the rotation will occur about an inertia axis or free axis of the body. However, if the rotor has a shaft journalled in bearings and is driven to rotate about the shaft axis, the axis of rotation is geometrically determined by the bearings or shaft and is a constrained axis of rotation, not necessarily identical with the free axis. The various known balancing methods serve essentially to determine and minimize any unbalance of the rotor so as to make the constrained axis of rotation as nearly as possible identical with the inertia axis. More specifically, the methods known as balance centering serve to first balance a rotor about its axis of rotation so that this axis satisfactorily coincides with the inertia axis, and then to drill a hole on the inertia-center points of the shaft or to otherwise mark the rotor, before subsequently machining the rotor on the same or on another machine about the coincident rotational and inertia axis thus marked. As a rule, for balance-centering purposes, the finished rotor is first mounted in a receiving device or cage journalled for rotation in oscillatorily supported bearings of a balancing machine. The rotor-cage assembly is then driven to rotate. Any unbalance, manifesting itself by oscillations of the bearings, is measured and minimized until during the measuring run, the free and inertia axis are coincident. Thereafter, the rotor is subjected in the same machine to a marking or machining operation by one or more center drills or other tools.

According to the method heretofore prevalent, the just-mentioned balance was obtained by displacing the rotor relative to the previously and individually balanced cage so as to make the free or inertia axis of the rotor coincident with the axis of rotation of the cage. Originally, this displacing of the rotor relative to the cage had to be effected while the machine Was at standstill, and the displacement had to be in accordance with an unbalance magnitude previously measured during a measuring run on the same machine. This method achieved its aim only gradually in increments so that much time was required. This was so because in most cases several consecutive displacing operations and just as many testing runs for checking the eifect of each individual displacement were necessary. However, in more recent machines the displacement of the rotor is effected during its rotation by motor means that participate in the rotation so that it is not necessary to stop the machine for each step of displacement. A cage assembly, including the displacing motors and mechanisms, all rotating together with the rotor, increases the total rotating mass to a multiple of the rotor mass alone. This affects the balancing accuracy so detrimentally that in many cases the requirements to be met cannot be satisfied despite all efforts and skill. Machines of this kind, therefore, are often applicable only for approximate balancing of raw workpieces, whereas the final balancing of the finished 3,l54,973 Patented Nov. 3, 1564 product must be carried out on a separate machine. This involves increased cost for investment, maintenance and labor. Further disadvantages of the described methods and corresponding machines reside in the fact that it is difficult to adapt the centering device to rotors of greatly varying length, and above all that the centering marks can be placed upon the rotor only with the aid of rotating tools while the rotor is at standstill. As a result, any geometric discrepancy between the carefully adjusted rotational axis of the rotor relative to the axis of rotation of the centering tool enters as an error into the balancing accuracy. As an inevitable consequence, the final machining about the marked axis of rotation, serving to finish the rotor, is not entirely free of balancing errors.

It is an object of my invention to minimize or eliminate the above-mentioned shortcomings of the known center balancing and similar machining methods and operations, and to provide a possibility of conducting such operations not only expeditiously, but also with a balancing accuracy and a reliability far greater than heretofore attainable.

To this end, and in accordance with one of the features of my invention, the geometric axis of rotation of a cage, chuck or other rotor-holding means of a balancing machine, is made to register with the inertia (free) axis of the accommodated rotor by imparting a balance producing displacement to the rotational axis of the holding means with the aid of displacement control devices not participating in the rotational measuring run; whereafter the machining, such as the application of centering marks to the rotor, is effected while the rotor is in rotation about its axis.

The method affords the balance centering of raw as well as partly finished or finished rotors with a heretofore infeasible degree of accuracy because, in the rotating assembly of rotor and holding means, the relative position of holding means and rotor remains fixed so that the driving torque is rigidly and most stifiiy transferred to the rotor, and also because the axis of rotation of the assembly can be displaced in lost-motion-free bearings in a sensitive and continuous manner until the measured unbalance vanishes. The unbalance thus to be eliminated is measured with any known balance analyzing devices suitable for this purpose, preferably with the aid of the conventional electric analyzing network and preferably by selecting the displacement planes, i.e. the geometric planes in which the corrective displacement of the axis of rotation is effected, as the reference planes, or correction planes of the unbalance measurement. Reference can be had to patent application Serial No. 426,424, filed April 29, 1954, now US. Patent No. 2,722,830, and US. Patent No. 2,706,399, issued April 19, 1955, for detailed information on electric analyzers suitable for use in conjunction with the present invention.

As mentioned, the marking of the axis of rotation of the rotor, or any other machining of the rotor about this axis, is carried out according to my invention while the rotor is kept in rotation about the axis after it has been determined by the above-described method of the invention.

According to one of the more specific features of the invention, for effecting the above-mentioned corrective displacements of the rotational axis of the assembly, I provide the balance-centering machine with a cam device that has eccentric cam faces coacting with the bearings of the rotatable rotor-holder assembly to permit continuous displacement of these bearings relative to the stationary machine frame structure. More specifically, for securing the desired displacement of the rotor-holder axis accurately free of lost motion, the eccentric cam faces are guided on lunette-type bodies whose semi-spherical surfaces permit these cam faces a self-alignment relative to the bearing faces of the rotating rotor-holder assembly.

According to further features of the invention, the masses of the rotor-holder assembly oscillating together with the rotor to be balanced, are compensated either by means of counteracting masses oscillating in opposition to the holder masses and directly excited by the adjusted eccentricity of the holder assembly, or by electric. means which produce compensating electromotive forces adjustable in such a Way as to have the indicating instrument show the rotor unbalance only.

There are two fundamental ways of applying the abovedescribed center balancing method according to the invention, the particular way selected depending upon the construction or type of the rotor to be processed.

(1) The Polar Coordinate Measuring and Displacing Method This method, like the polar methods previously known, requires the use of a phase transmitter, i.e. an alternating current generator such as a sine wave generator, which is connected with the rotor to rotate together therewith for producing two reference voltages 90 displaced relative to each other whose frequency corresponds to that of therotor revolutions. The angular position of unbalance is determined by rotationally adjusting the stator of the phase transmitter (311 in FIG. 3) and by also actuating the abovementioned displacing device according to the invention. Thereafter, the axis of rotation of the holderrotor assembly is displaced by the same displacing device in the manner above mentioned and more fully described hereinafter.

A mutual influencing of these two operating steps is prevented by the fact that the eccentricities adjusted by means of the displacing device are placed in registry with the two mutually displaced alternating currents taken from the phase transmitter. That is, one of these two voltages is coordinated with the angular position of the unbalance, whereas the other voltage is coordinated to the magnitude of the unbalance as well as to the eccentricities required for the correction of the unbalance.

According to another feature of the invention, the angular position can be found in a simple manner by adjusting the rotor and simultaneously the stator of the phasetransmitting generator with the aid of a differential gearing relative to the eccentric cam faces of the displacing device until, during the testing run of the rotor-holder assembly, the measuring instrument then connected with the phase transmitter no longer shows an unbalance indi cating deflection. The subsequent zeroing of this deflection during the same measuring run, effected by displacing the rotor axis with the aid of the eccentric cam faces of the displacing device, then produces the measure of the unbalance magnitude and hence the amount of the required unbalance compensation. The adjustments required during such a measuring run of a machine designed and operating according to the invention may be limited to turning two displacement control knobs or handles in the direction and by the amount required to set the rotor to the correct machining position.

The application of the polar method is recommended for centering operations in a single correction plane, that is if, for instance, a unilaterally journalled (flying) discshapcd rotor bodyis involved (see F168. 4 to 5b). The polar method is further of advantage for balancing in two correction planes of a rotor body journalled in two oscillating centering devices (see 5168. 1a to 3).

(2) T he Fixed-Coordinates Method This measuring and displacing method deals with on balance compensation relative to two predetermined coordinate planes of the rotor. For this purpose, the in vention provides a displacing device that permits performing the displacement of the axis of rotation in two component directions, preferably 90 mutually displaced,

the displacement in each direction being independent of that in the other direction. This method possesses several peculiar advantages, namely that the component of displacement can be combined with the component indication, that none of the individual component displacements affects the indications for the other components, and that if desired, the axis of the rotor may be permitted to perform parallel movements as well as tilting and tumbling movements. The method is suitable for singleplane balancing (see FIGS. 16:: to but is particularly well applicable for two-plane cantilever balancing (see FIGS. 6 to 10) because the components for the two planes accurately correspond to each other respectively.

in machines according to the invention, the rotorholder, when adjusted by displacement of its axis of rotation to establish balance of the assembly, comprises eccentrically located parts whose masses participate in the unbalance oscillations. According to another feature of the invention, this error mass is compensated by a corrected mass which oscillates in opposition to the error mass and whose movement is directly controlled by the adjusted eccentricity of the axis of rotation. However, the compensation may also be effected by electric means, for instance in the form of a counter EMF in the oscillation receiving or measuring instrument.

Other features of the invention, having for their object a fully automatic control of the balance-centering operation of a machine according to the invention, comprise novel controlling instrumentalities (FIGS. 14 and 15) and appertaining novel circuit connections (FIG. 13).

The invention, furthermore, comprises the combination of a machine tool for balancing with one for machining (FIGS. 16a to 160). These and other objects, advantages and features, the latter being set forth with particularity in the claims annexed hereto, will be apparent from, and will be mentioned in, the following description presented in conjunction with the embodiments shown by way of example on the accompanying drawings. In the drawmgs:

FIGS. 1a to Sc relate to a balance-centering machine for compensating unbalance according to the polar method by angularly adjusting a phase-position transmitter simultaneously with a spindle of the device for displacing the axis of rotation, FIGS. 1a to 3 applying to a bi-laterally journalled rotor such as a Cardanic shaft and FIGS. 4 and 5a to a unilaterally journalled or flying rotor such as a pump rotor. More specifically, FIG. la is a schematic front view of the machine seen from the operators position and serves to present the arrangement of all characteristic components of a balance centering machine for Cardanic shafts according to the invention. FIG. 1b is a schematic circuit diagram for the electric control of the machine. FIGS. 2a to 2 illustrate parts of the axis displacing device according to the invention on a larger scale. FIG. 2a represents a cross section through the housing Hi5 taken at the right-hand side of FIG. 2a, and illustrating a ball bearing between the housing and sleeve. FIG. 3 is a lateral view of one of the bearing standards of the machine according to FIG. la and also shows the control members located Within the standard. FIG. 3a is a detail end view of the differential gearing and worm gear 324 of FIG. 3; FIG. 3b is a diagrammatic detail plan view of the shafts and associated structure for adjusting Worm 324 from knob 312.

FIG. 4 is a longitudinal axial section through the axis displacing device of a balance centering machine according to the invention for unilaterally journalled (flying) rotors; FIG. 4a is a diagrammatic representation of the displaceable bearing unit showing the different axes and the efiect of displacement of the control spindle; and FIG. 5a is a cross section taken along the line VV in FIG. 4 in the direction of the arrows.

FIGS. 5b and 5c show a perspective view and a circuit diagram respectively of an example for a generally appliline VIIVII in FIGS. 6 and 8. FIG. 8 is a section along the line VIHVTII in FIG. 7a, but shown on a somewhat larger scale. FIG. 7b shows a special adjusting device. FIGS. 9 and 9a are perspective views on a larger scale, FIG. 9b is an aXially sectional view, and FIG. 10 is a perspective view of some of the parts applicable for the machine according to FIGS. 6 and 7a. FIGS. 11, 11a and 12 are explanatory and relate to the axis displacement as occurring when measuring and compensating unbalance in accordance with the fixed-coordinates method.

FIG. 13 shows a schematic circuit diagram for the fully automatic control and operation of a balance centering machine according to the invention, and FIGS. 14 and 15 illustrate a lateral view and front view respectively of a contact device appertaining to'the system of FIG. 13.

FIGS. 16a, 16b and 16c illustrate respectively a front view, a lateral View and a detail of a balance centering machine tool.

In general, the reference numerals used in the illustrations have three or four digits and are so chosen that the initial digit or digits indicate the figure or group of figures from which a particular part is best apparent.

The balance centering machine 1%, according to FIG. 1a, has two bearings standards 1112 and 1% mounted on the foundation 101. The two standards enclose parts for the springy journalling of a rotor to be tested, for instance, the Cardanic shaft 164 with its linkage heads 1114a and 164i). Mounted on the standards are further the drive motors 311}, 31% (FIGS. lb, 3) for rotating the rotor to be tested, these motors being preferably located in respective housings 123 and 124. Also located within the standards are phase-transmitters 311, 311' (FIGS. lb, 3) which consists of generators of a sinusoidal reference voltage. The machine tools as well as the displacing devices with the aid of which the free inertia axis of the rotor and the axis of rotation of the rotor-holding means are made coincident with each other are mounted in the housings or bearing supports 105 and 106 (FIGS. 1a, 3). The extent of the displacement required for eliminating all unbalance oscillations in the selected reference planes can be accurately determined with any of the unbalance measuring and indicating devices customary in the balancing technique. In the illustrated examples, for instance, the unbalance oscillations are transmitted to permanent-magnet oscillation pickups 1112 and 1113 (F168. 1a, 1b, 2a) located on the bearing standards 1132 and 103 respectively. For determining and for indicating the amount and angular position of the unbalance, the illustrated machine is shown equipped with wattrneters or similar instruments likewise as known and customary for such purposes. (See U.S. Patent 2,706,399, referred to above.) A wattmeter 115 serves for indicating the magnitude of the unbalance, and a second wattmeter 116 (FIGS. 1a, 1b) for indicating the angular position of the unbalance. The field coils of the wattmeters are supplied with alternating voltage from the two generators 311, 311 which operate as the phase transmitters (see field coils 1150, 115d and generator 311 in FIG. 3). The moving coils of the two wattmeters are supplied with curernt from the oscillation pickups 102 and 103'. Each drive motor 31% or 310' is coupled with one of the phase transmitter generators 311 or 311 (FIG. 3) to form a single set together therewith, so that the phase transmitting generators run in synchronism with the rotor 1134. Each generator produces two sinusoidal reference voltages, 90 phase-displaced from each other, at the frequency of rotor rotation. As

will be described below with reference to FIG. 3, the housing and hence the stator of each of the two generator sets is rotatable about the generator axis in order to thereby determine the angular position of unbalance in the known manner.

The above-mentioned displacement of the axis of rotation in accordance with a previously effected indication of unbalance is carried out with the aid of a displacing device on each of the two standards. The two displacing devices are operated manually by knobs 111, 112 (FIGS.

1a, 2a, 3) on the left housing 1% and right housing 1%, respectively; or the two displacing devices are placed in operation at a central location by means of switches 117 to 120 or automatically according to FIGS. 13 to 15.

For this purpose, remote control means 121 (FIG. la), for instance electric leads, flexible shafts or the like, are provided which are connected with the displacing means located in the housings 1115, 1116. The indicating instruments 115, 116, the control switches 117 to 120, and power switches 151, 151a, 151b, 1510 (FIG. lb) for controlling the drive motors, and a two-position switch 140 (FIGS. 1a, lb) which adjust the measuring device to the lefthand or right-hand reference plane E or E of the rotor, are preferably all accommodated within a separate control desk 122 (FIG. la). The reference planes E E extend perpendicularly to the plane of illustration and intersect the rotor at the respective locations denoted by E and E in FIG. 1a.

The tools for producing the centering marks or for otherwise machining the heads of the Cardanic shaft 1% are likewise contained in the housings 1115 and 1%. The axially movable spindles or holders 128 and 12% for these .tools project out of the respective housings (FIGS. 10.,

The rotor drive motors 311i, 319', each together with a differential gearing 3211 (FIG. 3) are mounted within the housings 123 and 124 on the bearing standards 1G2, 103 respectively. The driving torque is transmitted to the rotor-holding device ZQS-Zdfia and thus onto the rotor 1114 by means of a sprocket chain transmission 125 (FIGS. la, 3). The forward and reverse feed of the two centering tools is effected by means of a motor 13% (FIG. 1a) located within the machine base 101. Motor 1311 acts upon the tools with the aid of threaded spindles 131, 132 (FIGS. 10:, 3) engaged by threaded nuts 133 and 134 which are connected with double-armed levers 135 and- 136 respectively. The levers have a fixed pivot point 137 or 138 on the respective bearing standard and extend upwardly to the tool holders 128 and 129 respectively. Revolution of the screw spindles 131 and 152 causes the upper ends of the levers 135 and 136 to move uniformly inwardly, that is toward each other, or in the opposite direction, thus causing the tools to move toward or away from the linkage heads of the Cardanic shaft 1 34.

Two handles or knobs 312 and 314 (FIGS. 1a, 3) form part of devices with the aid of which the position of the rotor being tested can be adjusted relative to the axis displacing means as will be described below. The rotorholding means comprise two flanges 2115a and 20612 which receive the Cardanic shaft heads 1114a and 111% respectively.

According to the circuit diagram of FIG. 1b, the measuring and indication of rotor unbalance is carried out by means of an electric network 153. Such a network is generally known and is in most cases employed on industrial and commercially available balancing machines. For that reason, the details of such an analyzing network are not illustrated or described in this specification. When the switch 151 and its component switches 151a, 1511? and 1510 are placed in the measuring position in, and when the main power switch 152 is closed so that the rotor rive motors 3115, 3111' together with the respective phase transmitting generators 311, 311' are energized from the currentsupply line, then the rotor 1114 to be tested will run at a high speed of rotation (speed of normal operation).

The machine is now ready for the measuring runs. The unbalance analysis is effected sequentially in the predetermined reference planes E and E (FIG. la) of the Cardanic shaft heads ltl ia and llldb, respectively; that is, the unbalance is measured for each individual reference plane in two mutually perpendicular coordinate directions. At first, the measuring device is set for the left plane E. For this purpose, the switch r449 (FIG. lb) is turned to the left-hand position I (indicated by a broken line). As a result, the two voltages generated in the two pick-ups 302 and 1% can operate in the proper proportions through the electric network 153 onto the moving coils (not illustrated) in the respective wattmeters I115, 116 in such a manner that the unbalance oscillations occurring in the right reference plane E have no influence upon the measuring result derived from the unbalance oscillations in the left reterence plane E With the justmentioned setting of switch Edi), the switch 154 is simultaneously so placed that the voltage generated by the left phase transmitting generator 311 is supplied to the field coils (likewise not illustrated) of both wattmeters in such a manner that the wattmeter 155 receive the voltage corresponding to the vertical unbalance component whereas the wattmeter H6 receives the voltage corre sponding to the horizontal unbalance component.

For measuring unbalance in the other reference plane E the switch 140 is moved to the right position 1'. As a result, the system is set for analogous operation with reference to plane E Now the phase transmitter 311' supplies its voltages to the wattmeters 115, 115.

When in the different measurinr positions and settings of the system, the indication of the wattrneter 116 is turned to zero with the aid of-the axis displacing devices according to the invention and still to be described with reference to FIG. 3, then the wattmeter 115 indicates the magnitude of unbalance in the selected coordinate measuring direction. This indicated unbalance magnitude resents the amount of displacement required for the axis of rotation 25a (FIGS. 2a, 2b) of the rotor-holder shaft 205, which displacement will cause this indication to vanish. When in this manner, the indications for all measuring directions have been made to disappear, then the free or inertia axis of the rotor is coincident with the axis of rotation for the combined rotor-holder shaft and a rotor as a unit. The correct machining position for the rotor is thus attained. This latter axis of rotation of the combined rotor-holder shaft and rotor is not necessarily the central axis of shaft 285 per so, but is the axis of rotation for the combined rotor-holder shaft and rotor as a unit and is, after balancing, coincident with the axis of the tool holder 12% about which the central axis ine or 212s of spindle 412 or 21 rotates in its displaced position necessary to achieve the balance condition. For performing the centering work or machining operation, the switch 151 (FIG. lb) can now be placed to the centering position 0. This supplies current to the drive motor ran (FIGS. 1a, lb) for the marking tools, and the rotor drive motors 3%, Fill) are automatically switched to a lower speed of rotor rotation suitable for the marking operation.

FIG. 2a shows on a larger scale a side view, partly in section, of the left Cardanic shalt head 1534a, its coupling with the drive shaft 2% of the rotor-holding device,.the appertaining machining tool 2G3, and the axis displacing means for the head, the latter means being disposed within the housing 195. The tool-holder spindle 123 is surrounded by the hollow drive shaft of the rotor holder. On the side facing the rotor to be tested, the hollow shaft Elle carries the receiving flange 2 36!: to which the Cardanic shaft head ltl la is secured by means of several screws 287, 267'. The coupling between the drive shaft 235 of the holding device and the rotor 1% is completely rigid or still as far as the transmission of torque is concerned. Located on the side opposite rotor is a sprocket wheel 32511" which is driven by the sprocket chain 125 (see FIGS. and 3). Two ring-shaped sleeves and Elli are provided for journalling the hollow shaft 2G5 Within a cam spindle 212 of the displacing device. In the illustrated example, the marking of the rotor is effected by turning a centering face 284 into the shaft head with the aid of a cutting tool 2593 mounted on the tool holder spindle 123 which is axially displaceable with respect to guiding sleeves 2G1 and 2% which are rotatable within ball hearings in the housing 1% (FIG. 2a). The tool holder spindle 12 8 is moved into and out of the working position by means of the above-described linkage actuated by motor 13%. The tool holder 128 rotates together with the hollow driving shaft 205, butthe latter is radially displaceable with respect to the former. However, sleeve member Zill may be nonrotatable with respect to the im movable housing 1635.

For the processing of rotors not involving a Cardanic joint, for instance crank shafts, the rotor-receiving parts on flange Ztlda are preferably given an articulate design. An example of this kind is illustrated in FIG. 2b. The end of the rotor specimen 1M is hung, by means of a clamping head 2&8, into a Cardanic linking device 229 on flange Edda. Otherwise the specimen holding means in this example are imilar to those illustrated in FIG. 2a. The specimen 1M is given a centering hole 264 with the aid of a non-rotating drill or cutting tool 263', corresponding to the drill 721 shown in FIG. 7a.

The above-mentioned hollow spindle 23 .2 forms part of the device which according to the invention serves to displace the inertia axis of the rotor so as to make it coincident with the axis of rotation which in the balanced condition then coincides with the axis of tool holder 12S. Tool holder 128 does not participate in the rotational movement of the rotor. The hollow spindle 212 is provided with two eccentric surface portions or cam areas 213, 214. In the embodiment according to FIG. 2a, these two cam faces are designed as respective shoulder portions of the spindle 212 and both have the shape of circular cylinders whose respective axes have an inclined position relative to the spindle axis. The two cylinders have the same diameters, the same height and the same angle of inclination. Each eccentric cam face of the hollow displacement control spindle 212 is preferably located in four lunette-type guiding bodies uniformly distributed over the circumference of the cam face. The guiding bodies comprise semi-spheres 217, 217"" and 218', 218" located in respective pans 215, 2.15" and 216, 216". While only the guide bodies 215', 216' and 215", 216 as well as the semi-spheres 217', 218' and 217", 218" are visible in FIG. 2a, it will be understood that the semi-spheres or lunettes and the corresponding pans at each cam area are arranged in two pairs in the same manner as shown in FIG. 5a for the lunette pans denoted by 415. Each two pairs or" lunette-typeguides on the right and on the left side, in the illustrated example (FIG. 2a) the two upper guides 215' and the two guides 218' are mounted in fixed relation to the housing 05. The remaining pairs are axially displaceable in the housing 195. axis displacing device does not participate in the measuring run of the specimen rotor, but remains stationary with the exception of the adjusting movement in the axial direction which amounts to only a few millimeters. For this purpose, the pans 215 and 216" are arranged on a slider 228 which is axially displaceable along the inner wall of the housing 1W5. Displacement of the slider is effected by means of a screw spindle 229. This spindle is in threaded engagement with a lug 223a of the slider and is revolvably mounted in a lug 22E of housing which forms a fixed bearing. Bevel gears 231 and a shaft 232 form a connection between the adjusting spindle 22? and the adjusting knob ill, with the aid of which the adjustment of the slider 22% can be conveniently and accurately effected.

Consequently, the

212, as will be described with reference to FIG. 3, can be turned about its longitudinal axis on the sleeves 2%, 216 (FIG. 2a).

FIGS. 20 and 2d each show on a larger scale a side view and a cross section respectively of a somewhat modified lunette-type guide which, in contrast to the embodiment of FIG. 2a, possesses relatively large gliding surfaces, thus aflfording the advantage of reduced wear and a more reliable guidance of the cam face spindle. The slanting cylinder portion 213 of the spindle 212 rests in a lunette 222 whose guiding face is adapted to the exterior surface of the slanting cylinder and may be provided with an oil groove 222a. For security of mounting, these lunettes are guided by means of lugs 2221') in a guiding slot 222d either of the displaceable slider 223 and are made easily movable by providing a roller 222a on the lug 222i). The upper lunettes, such as those denoted by 217' and 218' in FIG. 2a, may be mounted in the same manner within guiding slots corresponding to slot 222d in FIGS. 20, 2d, but located in the respective fixed holders 215 and 216' respectively.

According to the modified embodiment shown in FlGS. 2e and 2], in a partly sectional view and in cross section respectively, similar lunettes 222 are supported on barrelshaped rolling bodies 242 within a cage 241; and ball bearings 243 are provided between the lunettes and the cam face spindle for further reducing the friction and permitting a fine adjustment of utmost sensitivity. Otherwise, the mounting corresponds to that described above with reference to FIGS. 20 and 2d.

The lunette-type guiding devices have the advantage of journalling the cam face spindle 212 of the displacing device completely free of lost motion. Conseqaently, the possibility of any movement in the bearings during the measuring and machining run, which may detrimentally affect the balancing accuracy, is completely eliminated.

FIG. 3 shows the left-hand bearing standard 102 according to FIG. In on a larger scale and partly in section in order to how details of the driving members housed within the standard. The standard 1&2 rests upon the machine base 101 to which it is fastened by bolts 391. Two vertical leaf springs 393' and 3&3", located one behind the other as viewed in FIG. 3 and corresponding to the leaf springs 593' and 583" shown in FIG. 5a, are firmly secured to the standard by means of screws 3% (F1 3. 3). The leaf springs support the housing 1&5 so as to permit horizontal oscillations of the housing perpendicular to the plane of illustration, hence toward and away from the observer, while rigidly holding the housing in the vertical direction. The housing 105 is joined with the leaf springs by means of screws 395. As in FIGS. 1a and 2a, the tool spindle is denoted by 128, and the coupling flange for the rotor to be tested is denoted by 2136a. The described axis displacing means can be actuated from the control desk 122 (FIG. 1a), or automatically, or by means of the knob or handle 111 (FIG. 3). Located between the springs 3tl3' and 383" of the bearing standard is the driving unit which comprises the motor 319 and the phasetransmitter 311 coupled with the motor, as well as the differentiai g earing 320. Denoted by 135 is the doublearmed lever according to P16. la. As explained, the lever 135 is turned about its pivot 137 by displacement of the nut 133 relative to the screw spindle 131 with the effect of shifting the tool holding spindle 128 axially inwardly or outwardly.

The take-off shaft Sitib of the differential gearing 32b is journalled in two axially spaced places and carries on its free, projecting end the sprocket gear 325a for the chain transmission 125 which connects the shaft 31% with the upper sprocket 325a" and thus with shaft 265 (FIG. 2a) and rotor-receiving flange 296a.

The differential gearing 32% serves to place a measured angular unbalance position of the rotor, for instance of Cardanic shaft 1-94, in registry with the measuring component indicated by one of the two wattmeter instruments id or 116. This is done by turning the rotor to be tested as well as the housing of the phase-transmitter generator 311 (FIG. 3) relative to the control spindle 212 (Fi'G. 2a) of the displacing device. This adjustment is carried out by turning the knob 312 (FIGS. 3, 3a, 3b) in one or the other direction. The rotation of knob 312 is transmitted by a shaft 3% and a bevel gear 3%:1 to a bevel gear 322a on an auxiliary shaft 321 which carries two further bevel gears 322k and 3220. Bevel gear 322d acts through a bevel gear upon a shaft 322) which carries a worm meshing with a worm gear 324 of the differential gearing 32%. As a result, the rotary displacement of knob 31?. is transmitted to the worm gear 324 of the diiierential gearing.

Mounted between the shaft 310a of the drive motor it; and the diiferential gearing 326 is a transmission composed of three spur gears Iiltlc, which compensates the reversal rotation initiated from the difierential gearing. The differential gearing comprises a driving pinion 326 loosely fitted on the shaft 3319b, and a take-oil pinion 328 which is coupled with the sprocket gear 325]). The differential gearing further comprises a gear 327 which is revolvably mounted in the housing of the differential gearing and in mesh with the driving and take-off pinions. Pinion 325 is driven from the motor shaft 310a through the transmission gearing 515. The bevel gear 3220 controls the angular displacement of the rotatable stator of the phase transmitter 311 through shaft 322e and worm 3212a". The take-off pinion 328 imparts rotation to the sprocket gear $2551 and, by means of the chain 126, also to the sprocket gear 325i)" on the cam face spindle 212 (FIG. 2a) of the displacing device. The rotation thus imparted to the displacement control spindle 212 occurs in a direction depending upon the adjustment of the worm gear 324 (FiG. 3) effected by the operation of the control knob 31?. (FIGS. 3a, 3b). This direction of spindle rotation is such that the peak of the eccentric control faces 213, 2-14 on the spindle 212 (FIG. 2a) can be given a leading or lagging setting relative to the measured angular position of unbalance in the rotor 1G4 driven by the drive shaft 2%. Simultaneously and in the same direction and degree, the stator of the phase transmitter 311 is turned so that the said peak points remain in the component direction. The just-mentioned peaks of the displacement controlling cam faces are their highest points above the geometric axis of rotation 205a (FIG. 2a) or" all rotating parts. a

The bearing standards NZ and 103 (FIG. In) as Well as the parts housed therein are accurately similar to each other. That is, the right-hand bearing standard 103 is symmetrical to the above-described bearing standard 102. The operating knob 112 or" standard res corresponds to the knob 111 of standard 102, and knob 314 corresponds to knob 312.

While the functioning of the machine during a balancecentering operation is essentially apparent from the foregoing description, a summarizing example of a complete machine operation will now be given.

The rotor specimen 1% (FIG. 1-01) to be center balanced is first inserted and firmly mounted between the receiving flanges Ztlda, Zt'tb of the bearing standards 102 and 103, respectively, of which at least one may be displaceable relative to the machine base in order to adapt the machine to specimens of different length. After the rotor 104 is properly mounted, the switch 151 (FIGS. 1a, 1b) is placed into the position m for measuring.

In FIG. la, the switch 151 is shown as having two push-buttons to be selectively depressed depending upon whether the setting in or c is desired, whereas in FIG. 1b, for simplicity, the same switch is shown as a lever to be set to position in or c. When switch 151 is set to In, its associated component switches 151a and 15111 energize the respective terminal groups Tm of the two motors 31b and Sill. These motors are two-speed A.-C. motors. Accordingly, each has another group of terminals 

1. THE METHOD OF BALANCE-CENTERING A ROTOR, WHEREIN A JOURNAL IS PROVIDED FOR ROTATION OF THE ROTOR TO BE BALANCED, WHICH COMPRISES RIGIDLY MOUNTING THE ROTOR ON HOLDING MEANS IN A FIXED POSITION RELATIVE THERETO, ROTATING THE ROTOR AND HOLDING MEANS AS A RIGID UNIT IN SAID JOURNAL, CONTINUOUSLY ROTATING AND RADIALLY DISPLACING DURING SUCH CONTINUOUS ROTATION THE HOLDING MEANS AND ROTOR AS A UNIT RELATIVE TO SAID JOURNAL TO SHIFT THE AXIS OF ROTATION OF SAID UNIT INTO COINCIDENCE WITH THE INERTIA AXIS OF THE UNIT, AND DURING SUCH CONTINUOUS ROTATION COMPENSATING THE UNBALANCE FORCES CREATED BY THE RADIAL DISPLACEMENT OF SAID UNIT TO ESTABLISH A GIVEN BALANCE CONDITION ABOUT THE DISPLACED AXIS OF ROTATION, AND MACHINING THE ROTOR ABOUT THE DISPLACED AXIS OF ROTATION SAID DISPLACEMENT OF AXIS OF ROTATION OF SAID UNIT BEING INDEPENDENT OF THE AXIS OF THE TOOL PERFORMING SAID MACHINING. 